2003 SL 350 starting problem

[snowshredder]

had the car 12 months and now i'm getting problems starting it after short runs, starts outside house but after short run it won't fire up just turning over, had this a few times now, left it a while and tried again a few times over and eventually it started up, the other day i was outside a motorbike shop and it happened, a mechanic came out with a tin of ptfe cable guard spray and sprayed a quick spurt up each air trunk after explaining to me it's how they start troublesome bikes lol and it fired right up, i think that was luck though. car is not hot or at running temp too

I,m guessing a camshaft or crank sensor ?? the fuel pump can be heard ok too, any other ideas ??